About: Back up LVM xen guest containing lvs

Hello!
I have a question regarding the last part of the How To where it warns to make sure and unmount the volume, then delete the device map created by kpartx.

In my case I do not have a xen guest containing LVs, but I have a Windows Xen guest with an NTFS formatted volume. I am able to create the device with kpartx and mount the partition using ntfs-3g. So there's no problem there.

My question is, can the file system become corrupt if I am only mounting the partition of the Xen Guest as read only?? I'd like to leave the filesystem mounted for periodic backups from the Centos 5.4 host. Is that a bad idea? If so, can someone point me to a "why this is a bad idea" type of document/page? Thanks a bunch! I'm trying to determine if there are cases where the file system becomes corrupt that don't apply to my setup since I don't have LVs inside of a guest.